I have been wrestling with my Times font and why it displayed italics as bold. Looking around here on the forum I chanced on a suggestion to use the exact name of the font. For example, the file for a Times font on my hard drive is named times.ttf, but the actual name of the font is Times New Roman. So renamed the files and, lo and behold, it works. Don't ask me why, I can't say the delectable option to add fonts of your own on the Kobo has been made easy, but here you go...

Thanks for this renaming tip. I wondered why some of the fonts you linked to in post #26 had this bold-instead-of-italic problem. I've just tried the problem ones again with different names and they now work